[PATCH v3] i2c: enable runtime PM for I2C adapter devices enumerated from ACPI

[Rafael J. Wysocki]

On Monday, September 30, 2013 07:20:59 PM Rafael J. Wysocki wrote:
> On Monday, September 30, 2013 05:43:48 PM Mika Westerberg wrote:
> > The ACPI specification requires the parent device to be powered on before
> > any of its children. It can be only powered off when all the children are
> > already off.
> > 
> > Currently whenever there is no I2C traffic going on, the I2C controller
> > driver can put the device into low power state transparently to its
> > children (the I2C client devices). This violates the ACPI specification
> > because now the parent device is in lower power state than its children.
> > 
> > In order to keep ACPI happy we enable runtime PM for the I2C adapter device
> > if we find out that the I2C controller was in fact an ACPI device. In
> > addition to that we attach the I2C client devices to the ACPI power domain
> > and make sure that they are powered on when the driver ->probe() is called.
> > 
> > Non-ACPI devices are not affected by this change.
> > 
> > This patch is based on the work by Aaron Lu and Lv Zheng.
> > 
> > Signed-off-by: Mika Westerberg <mika.westerberg at linux.intel.com>
> > ---
> >  drivers/i2c/i2c-core.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 46 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> > index 29d3f04..fa861ad 100644
> > --- a/drivers/i2c/i2c-core.c
> > +++ b/drivers/i2c/i2c-core.c
> > @@ -236,6 +236,27 @@ int i2c_recover_bus(struct i2c_adapter *adap)
> >  	return adap->bus_recovery_info->recover_bus(adap);
> >  }
> >  
> > +static void acpi_i2c_device_pm_get(struct i2c_client *client)
> > +{
> > +	struct i2c_adapter *adap = client->adapter;
> > +
> > +	/* Make sure the adapter is active */
> > +	if (ACPI_HANDLE(adap->dev.parent))
> > +		pm_runtime_get_sync(&adap->dev);
> > +	if (ACPI_HANDLE(&client->dev))
> > +		acpi_dev_pm_attach(&client->dev, true);
> 
> It would be sufficient to do
> 
> 	if (ACPI_HANDLE(&client->dev)) {
> 		pm_runtime_get_sync(&adap->dev);
> 		acpi_dev_pm_attach(&client->dev, true);
> 	}
> 
> here (and below), because I don't think the client with an ACPI handle and the

s/I don't think/I think/

> parent without one is extremely unlikely (to the point of non-existence
> actually ;-)).  And even if something like that happens, then we only enable
> runtime PM for the adapter if the parent has an ACPI handle, so it still should
> be OK.
> 
> Apart from this the patch looks good to me.
> 
> > +}
> > +
> > +static void acpi_i2c_device_pm_put(struct i2c_client *client, bool detach)
> > +{
> > +	struct i2c_adapter *adap = client->adapter;
> > +
> > +	if (ACPI_HANDLE(&client->dev) && detach)
> > +		acpi_dev_pm_detach(&client->dev, true);
> > +	if (ACPI_HANDLE(adap->dev.parent))
> > +		pm_runtime_put(&adap->dev);
> > +}
> > +
> >  static int i2c_device_probe(struct device *dev)
> >  {
> >  	struct i2c_client	*client = i2c_verify_client(dev);
> > @@ -254,11 +275,15 @@ static int i2c_device_probe(struct device *dev)
> >  					client->flags & I2C_CLIENT_WAKE);
> >  	dev_dbg(dev, "probe\n");
> >  
> > +	acpi_i2c_device_pm_get(client);
> > +
> >  	status = driver->probe(client, i2c_match_id(driver->id_table, client));
> >  	if (status) {
> >  		client->driver = NULL;
> >  		i2c_set_clientdata(client, NULL);
> >  	}
> > +
> > +	acpi_i2c_device_pm_put(client, !!status);
> >  	return status;
> >  }
> >  
> > @@ -271,6 +296,8 @@ static int i2c_device_remove(struct device *dev)
> >  	if (!client || !dev->driver)
> >  		return 0;
> >  
> > +	acpi_i2c_device_pm_get(client);
> > +
> >  	driver = to_i2c_driver(dev->driver);
> >  	if (driver->remove) {
> >  		dev_dbg(dev, "remove\n");
> > @@ -283,6 +310,8 @@ static int i2c_device_remove(struct device *dev)
> >  		client->driver = NULL;
> >  		i2c_set_clientdata(client, NULL);
> >  	}
> > +
> > +	acpi_i2c_device_pm_put(client, true);
> >  	return status;
> >  }
> >  
> > @@ -294,8 +323,11 @@ static void i2c_device_shutdown(struct device *dev)
> >  	if (!client || !dev->driver)
> >  		return;
> >  	driver = to_i2c_driver(dev->driver);
> > -	if (driver->shutdown)
> > +	if (driver->shutdown) {
> > +		acpi_i2c_device_pm_get(client);
> >  		driver->shutdown(client);
> > +		acpi_i2c_device_pm_put(client, false);
> > +	}
> >  }
> >  
> >  #ifdef CONFIG_PM_SLEEP
> > @@ -1263,6 +1295,16 @@ exit_recovery:
> >  	bus_for_each_drv(&i2c_bus_type, NULL, adap, __process_new_adapter);
> >  	mutex_unlock(&core_lock);
> >  
> > +	/*
> > +	 * For ACPI enumerated controllers we must make sure that the
> > +	 * controller is powered on before its children. Runtime PM handles
> > +	 * this for us once we have enabled it for the adapter device.
> > +	 */
> > +	if (ACPI_HANDLE(adap->dev.parent)) {
> > +		pm_runtime_no_callbacks(&adap->dev);
> > +		pm_runtime_enable(&adap->dev);
> > +	}
> > +
> >  	return 0;
> >  
> >  out_list:
> > @@ -1427,6 +1469,9 @@ void i2c_del_adapter(struct i2c_adapter *adap)
> >  		return;
> >  	}
> >  
> > +	if (ACPI_HANDLE(adap->dev.parent))
> > +		pm_runtime_disable(&adap->dev);
> > +
> >  	/* Tell drivers about this removal */
> >  	mutex_lock(&core_lock);
> >  	bus_for_each_drv(&i2c_bus_type, NULL, adap,
> > 
> 
> Thanks!
> 
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.